15785-54-3

4-Hydroxy-3-methoxy-5-nitrobenzoic acid is used as an intermediate for Opicapone. Opicapone is a catechol-O-methyltransferase (COMT) inhibitor used to increase the availability and duration of action of L-Dopa, the standard of care for Parkinson's disease.

The general procedure for the synthesis of 4-hydroxy-3-methoxy-5-nitrobenzoic acid from vanillic acid was as follows: vanillic acid (20 g, 119 mmol) was dissolved in acetic acid (200 mL) and 60% nitric acid (9.7 mL, 126.4 mmol) was added slowly and dropwise. The reaction mixture was stirred at room temperature for 30 min and then poured into ice water to quench the reaction. The precipitate precipitated was collected by filtration, washed well with water and dried under vacuum to afford the target product 4-hydroxy-3-methoxy-5-nitrobenzoic acid as a yellow powder. The yield was 11.28 g (44% yield) and the melting point range was 216-219 °C (literature value 216 °C).

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